1. Field of the Invention
The present invention relates to a Light Emitting Diode (LED), and more particularly, to a dipolar LED structured to concentrate light emission in both lateral directions and an LED module incorporating the same.
2. Description of the Related Art
According to the development of electronic devices, Liquid Crystal Displays are gaining attention as next generation display devices. Since an LCD does not light spontaneously, it is required to provide a backlight unit for generating light in rear of an LCD panel.
FIG. 1 is a cross-sectional view illustrating a Light Emitting Diode (LED) lens disclosed in U.S. Pat. No. 6,679,621 as an example of a conventional side-emitting LED used in the LCD backlight unit.
Referring to FIG. 1, an LED lens 10 disclosed in the above document includes an upper part having a reflecting surface I and a refractive surface H and a lower part having a refractive surface 156. In a three dimensional view, the LED lens 10 is configured symmetric about an optical axis 43.
In this LED lens 10, light generated from a focal point F is radiated to the outside through the refracting surface H after reflecting from the reflecting surface I or directly through the refracting surface H.
However, the conventional LED lens 10 has following drawbacks.
First, in an LED array including a plurality of LED lenses 10K, 10L, 10M, 10N and so on as shown in FIG. 2, when an LED lens 10L has a light radiation pattern or simply a light pattern LP10 as shown in FIG. 2, a portion of light directly collides against adjacent LED lenses 10K and 10M so that the adjacent LED lenses 10K and 10M screen the light portion thereby forming blocked areas BA10. The blocked area BA10 causes loss to light emitted from the LED lens 10L. Then, the LEDs are necessarily increased in number corresponding to the light loss by the blocked areas BA10, thereby obstructing the miniaturization of the LCD backlight.
Another problem of the conventional LED lens 10 will be described with reference to FIG. 3.
As shown in FIG. 3, it is frequently required to increase the size of an LED chip 2a over that of the existing LED chip 2 in order to reduce current density thereby improving luminous efficiency. However, light beams L2 generated in the periphery of the LED chip 2a are out of total reflection condition and thus emitted upward without reflecting from the reflecting surface I. This disadvantageously lowers the color uniformity of an entire LCD backlight module. Although the poor uniformity can be improved by increasing the size of the LED lens 10, the increased LED lens size also creates a problem of increasing the thickness of the LCD backlight unit.